SNOW AND EXPERIMENTAL METEOROLOGY 
the world. By using silver iodide in relatively insignifi- 
cant quantities, a situation could be developed under 
which ice crystals would immediately form in any cloud 
which formed in air colder than —5C. 
The anomalous effects which would follow from such 
an atmospheric condition are not predictable at the 
present time. It is obvious that important changes in 
storm patterns and climatic conditions could follow 
wherever these phenomena are governed by supercooled 
cloud structures. 
The Use of Seeding Techniques for Studying the At- 
mosphere. By placing a known quantity of dry ice or 
silver iodide in a supercooled cloud it is possible to 
“mark” a cloud in such a way that subsequent changes 
in the physical nature of the cloud may be followed in 
great detail and with an accuracy hitherto impossible 
to achieve. By this method, the development of turbu- 
lence, the growth characteristics of snow crystals, the 
chain reaction mechanisms responsible for the develop- 
ment of widespread snowstorms, the change of insola- 
tion from cloudy sky to clear sky, the formation of new 
clouds, the development of precipitation, the occurrence 
of supersaturation, the properties of false cirrus, and 
many other atmospheric phenomena may be studied in 
great detail. Since it is possible to initiate many of these 
processes, it is possible for the first time to follow a 
particular meteorological process from beginning to end. 
As experience is gained in this field, it is likely that 
these techniques will be most valuable in permitting us 
to reach a better understanding of that very complex 
but fascinating subject which we call weather. A careful 
scientific approach to these problems, using imagina- 
tion, enthusiasm, and sound judgment, is of utmost 
importance if success is to be achieved in this new 
aspect of experimental meteorology. 
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